Introduce globals for demonstration

99bottles.sh

 #   [99b]: http://99-bottles-of-beer.net/language-bash-1831.html
 #
 
+#
+# Default transition mode
+#
+# 'standard' to use the standard form; 'careless' to have the
+# song consider effects of gravity on the bottles.
+#
+# Default is 'standard'.
+#
+NN_BOTTLES__MODE=${NN_BOTTLES__MODE:-standard}
+
+#
+# Starting bottle amount
+#
+# Initial amount of bottles specified as numeral.  Numerals up
+# to 99 are supported.
+#
+# Default is 'ninety-nine'.
+#
+NN_STARTING_AMOUNT=${NN_STARTING_AMOUNT:-ninety-nine}
+
 pred() {
     #
     # Get predecessor to a number $1
 
 main() {
     local TransitionLine    # transition line between verses
-    local togo              # bottles to go
-    local mode=standard     # transition mode
+    local togo=$NN_STARTING_AMOUNT  # bottles to go
+    local mode=$NN_BOTTLES__MODE    # transition mode
     while true; do case $1 in
         --careless)     mode=careless; shift ;;
         *)              break ;;